A method for producing a semiconductor device includes a preparing step of preparing a board formed with a concave portion, a terminal disposed in or around the concave portion, and a semiconductor element disposed in the concave portion; a wire-bonding step of connecting the terminal to the semiconductor element with a wire; a pressure-welding step of pressure-welding an encapsulating sheet to the board so as to be in close contact with the upper surface of a portion around the concave portion and to be separated from the upper surface of the concave portion under a reduced pressure atmosphere; and an atmosphere releasing step of releasing the board and the encapsulating sheet under an atmospheric pressure atmosphere.